High levels of toxic chemicals have been found in stranded dolphins and whales along the southeastern coast of the United States, according to a new study published on Wednesday.
Arsenic, mercury and other chemicals were found in their bodies, giving more information on contaminant concentrations in dolphins and other toothed whales, researchers said.
Toothed whales include dolphins, porpoises and other whales like the melon-headed whale and the Cuvier’s beaked whale.
These toxic chemicals mostly enter the ecosystem from the burning of fossil fuels and mining, said Alistair Dove, vice president of research and conservation at the Georgia Aquarium in Atlanta. Dove was not involved in the study.
How these chemicals make their way through the ecosystem also has implications for people who enjoy eating the same types of fish these marine mammals consume.
Toxic chemicals and the food chain
Organisms lower on the food chain ingest the chemicals, which continue their way up through the food chain, getting more concentrated the higher up the chain they go, said Dr. Annie Page-Karjian, study author, clinical veterinarian and assistant research professor at Florida Atlantic University in Boca Raton.
When dolphins and whales eat fish with concentrations of the chemicals, the toxic elements enter their bodies. Dolphins eat a wide variety of fish, shrimp, jellyfish and octopus, and on the US East Coast, dolphins like to eat animals like herring, mackerel and flounder, said Page-Karjian.
Some of the same fish are also commonly eaten by humans, so the results of this study has given researchers insight into how the substances affect human health.
“If humans eat a lot of fish that contain too much arsenic and mercury, these metals can poison the liver and other organs, or cause neurological damage to the brain and nervous system,” Dove said.
Sex and geography affect toxicity levels
Researchers used liver and blubber samples from 11 different animal species to test for dozens of different substances between 2012 and 2018. The animals were found on shores in North Carolina and Florida.
Sex played a role in the levels of chemicals in dolphins, researchers found. For example, adult female bottlenose dolphins showed significantly higher levels of arsenic and lower levels of iron compared to their male counterparts.
Geography also had an impact. Dolphins found in Florida had higher concentrations of chemicals such as mercury and lead. In North Carolina, dolphins had higher concentrations of iron compared to the ones found in Florida.
Turning the tide
Humans can help heal the ocean over time to reduce the amount of toxicants in the marine environment, said Page-Karjian. Part of this includes decreasing the polluted runoff and chemicals in waterways from fossil fuels as well as reducing the use of single-use plastics.
Many plastic objects that humans use contain these dangerous phthalates, such as plastic packaging film, detergents and some children’s toys, according to the US Centers for Disease Control and Prevention.
“If we reduce the use of fossil fuels, we can slow the rate of climate change and put fewer pollutants into the ocean,” Dove said. “This applies to mercury, which most often comes from coal-fired power plants, and even plastics, which are ultimately produced from natural gas.”